One of the important targets for developing a causal therapy for Alzheimer's disease (AD) is represented by synapses. The nitric oxide/soluble guanylyl-cyclase/cGMP/cGMP-dependent-protein kinase/cAMP-responsive binding element (NO/sGC/cGMP/PKG/CREB) signaling pathway is thought to play an important role in the synapse during plasticity and memory. Preliminary data from my laboratory have demonstrated the involvement of the pathway in amyloid-beta-induced synaptic dysfunction. Most importantly, sildenafil, an inhibitor the cGMP-degrading enzyme phosphodiesterase V (PDE5), produces an immediate and long lasting amelioration of synaptic and memory abnormalities in an amyloid-depositing mouse model, the APP/PS1 animal. In addition, sildenafil re-establishes normal number of active boutons and glutamate-induced increase in active boutons in cultures from APP/PS1 mice. Thus, the overall purpose of this project is to identify molecules that, by enhancing the NO/sGC/cGMP/PKG/CREB pathway, re-establish normal cognition in the APP/PS1 mouse model. Our approach is to combine expertise in organic chemistry to generate new molecules acting on the signaling pathway with experience in neurobiology to test these compounds at multiple levels including hippocampal slices, neuronal cultures and in vivo animals. This strategy offers the advantage of screening novel drugs in a low cost and fast system (cell cultures), of validating their efficacy in a preparation with intact neuronal circuits (slice from APP/PS1 mice), and finally of determining whether they re-establish normal learning and memory in an in vivo complex neuronal system that is used as an AD model (the whole animal). The following aims will be addressed: a) to identify new enhancers of the NO/sGC/cGMP/PKG/CREB pathway that might be used in CNS diseases; b) to screen the new NO/sGC/cGMP/PKG/CREB pathway enhancers by selecting compounds that rescue amyloid-beta-induced synaptic dysfunction, c) to determine if treatment with novel enhancers of the NO/sGC/cGMP/PKG/CREB pathway have a beneficial effect on cognitive abnormalities in APP/PS1 mice. On the completion of these studies we will identify new therapeutic targets (PDE5, PKG1) and strategies (PDE5 inhibitors, PKG1 agonists) for the treatment of cognitive loss in AD. The whole project will be organized in clear milestones with objective success/failure criteria and GO/NOGO decision points. [unreadable] [unreadable] [unreadable]